67603900

Appears in sequences

• a(n) = (2n+1)!/n!^2.at n=12A002457
• a(1)=1; for n >= 1, a(n+1) = lcm(a(n),n) / gcd(a(n),n).at n=25A008339
• First numerator and then denominator of central elements of Leibniz's Harmonic Triangle.at n=25A046212
• Swinging factorial, a(n) = 2^(n-(n mod 2))*Product_{k=1..n} k^((-1)^(k+1)).at n=25A056040
• a(n) = n!/(k!)^2, where k is the largest number such that (k!)^2 divides n!.at n=24A056042
• a(1) = 1, a(n) = lcm(n, a(n-1)) / gcd(n, a(n-1)).at n=24A077139
• a(n) = n * binomial(n-1, floor((n-1)/2)) = n * max_{i=0..n} binomial(n-1, i).at n=25A100071
• (n-1)! divided by (product phi(d)! ; d divides n).at n=25A120066
• a(n) = 2^n*binomial((n + 1 + (n mod 2))/2, 1/2).at n=24A242172
• a(n) = A(n) if n is even else a(n) = A(n)*(n-1)/(n+1) with A(n) = ((n-1)!/ floor((n-1)/2)!^2).at n=25A274707
• Expansion of (1 + 2*x)/(1 + 4*x^2)^(3/2).at n=24A331552